Thin web

ABSTRACT

Embodiments of a thin web comprising a plurality of channels extending through the film are disclosed. The channels are in a substantially closed position but are capable of being in an open position to allow flow from the female side through the film to the male side. In certain applications, a greater pressure on the female side than the male side is capable of opening the channels. Embodiments may also include a thin web comprising a plurality of three dimensional apertures extending through the plastic film. The apertures may form a substantially closed channel defined by a sidewall and the channels being disposed at an angle greater than 70° with respect to a female side of the film. The thin web may be a plastic film or a thermoplastic film comprising a polyolefin, for example, or any other suitable material. The polyolefin may comprise at least one of polyethylene, polypropylene, low density polyethylene, or high density polyethylene, for example.

FIELD OF THE INVENTION

The present invention is directed to thin webs and methods of formingthin webs. The thin webs comprise apertures configured as preferentialflow valves capable of allowing substantially more liquid flow throughthe film in one direction than the other.

BACKGROUND

Vacuum formed films typically have a plurality of apertures that allowliquids and gases to pass through the film. Such films may beincorporated into disposable products, such as feminine hygieneproducts, diapers, incontinent products, hospital pads, bedding,breathable clothing and/or sleeping bag linings, for example. Suchproducts are typically composite structures comprising a top sheet foruse adjacent to the skin and an absorbent layer. An example of anapertured film for making disposable diapers is disclosed in U.S. Pat.No. 3,814,101, which is hereby incorporated by reference.

One method of forming apertures in thin webs or plastic film is byvacuum film forming, see U.S. Pat. No. 3,054,148 which is herebyincorporated by reference, for example. In this process, the plasticfilm lays on a rotating screen having a plurality of holes. The filmpasses over a vacuum chamber as the screen rotates creating a pressuredifferential on either side of the plastic film. The pressuredifferential causes the film to rupture at the holes in the screen toform the apertures. The holes in the screen may be in a specific patternor shape that transfers onto the film in the process. In this process,the heated film is supported by a screen and a vacuum applied to theunderside of the perforated screen. Holes are pulled in the film in thedirection of the vacuum beneath the screen thereby forming taperedcapillaries in the film.

Many methods and apparatuses for preparing plastic films comprisingapertures have been developed, examples include U.S. Pat. Nos.4,155,693; 4,252,516; 3,709,647; 4,151,240; 4,319,868; 4,388,056;4,950,511; 4,948,638; 5,614,283; and 5,887,543, which are all herebyincorporated by reference.

Conventional vacuum film forming process may comprise extruding moltenpolymeric materials such as polyethylene or other polyolefin through adie to form a hot melt web or by laying a previously formed thin web orplastic film on a screen. The hot melt web of polymer lays on a rotatingscreen mounted on a stationary vacuum drum. The vacuum drum has an axialslot and a set of seals extending longitudinally along the length of itsinside surface, beneath the area where the web of plastic impinges onthe screen or molding element. A vacuum is pulled on the inside thescreen to form the apertures in the film through the holes in thescreen. After the aperture is formed, air flowing through the film coolsthe film and sets the shape of the aperture.

The physical shape of the screen determines the geometric pattern ofapertures on the film and thus contributes to its aesthetic, tactile andmechanical properties. U.S. Pat. Nos. 5,897,543; 5,718,928; 5,591,510;and 5,562,932, which are all hereby incorporated by reference, describefilms, screens, and methods of forming films having apertures that formcapillaries extending through the film and the capillaries are disposedat an angle from about 5° to about 60° with respect to a plane that isperpendicular to a surface of the film. Accordingly, the films will havea masking characteristic such that the absorbent material is not asvisible to a user as when the capillaries are perpendicular to thesurface of the film.

There is a need for a thin web comprising apertures acting aspreferential flow valves. There is a need for a thin web that provides asignificantly greater resistance to flow of a liquid through the web inone direction as compared the flow of the same liquid in the oppositedirection.

SUMMARY

Embodiments of the thin web may be useful as a separator in a containerthat is comprises two sections. Such a container could be used toseparate a liquid from a solid such as fresh fruit from its juice. Asthe juice is released from fruit in one section of the container, thejuice may flow through the separator comprising a thin web withpreferential flow valves into another section of the container. Thejuice is then substantially trapped in the other section by thepreferential flow valves in the thin web.

Embodiments include a thin web comprising a plurality of channelsextending through the film, wherein the channels have a male side and afemale side. The channels are in a substantially closed position and arecapable of being in an open position to allow flow from the female sidethrough the film to the male side. In certain applications, a greaterpressure on the female side than the male side is capable of opening thechannels. Further in other embodiments, that may require a lower degreeof reverse flow, a greater pressure on the male side than the femaleside is capable of holding the channels in a substantially closedposition. Reverse flow in this application is flow in an undesireddirection such as, for example, from a section of a container containingreleased fruit juice to a section containing fruit.

Embodiments may also include a thin web comprising a plurality of threedimensional apertures extending through the plastic film. The aperturesmay form a substantially closed channel defined by a sidewall and thechannels being disposed at an angle greater than 70° with respect to afemale side of the film. In such embodiment, the sidewall may act as aflap to keep the aperture in a substantially closed position. The flapmay react to pressure or weight that is capable of opening or furthersealing the aperture as desired.

The thin web may be a plastic film or a thermoplastic film comprising apolyolefin, for example, or any other suitable material. The polyolefinmay comprise at least one of polyethylene, polypropylene, low densitypolyethylene, or high density polyethylene, for example.

Details of embodiments of the thin web are described in the descriptionbelow and the accompanying drawings. Other features and aspects of theinvention may be apparent based upon an understanding of the featuresdescribed and the nonlimiting examples.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a photograph of a container comprising honeydew melon piecessitting in melon juices;

FIG. 2 is a photograph of a container comprising a separation layerholding cantaloupe above the cantaloupe juices;

FIGS. 3 a, 3 b, and 3 c depict portions of embodiments of a plastic filmcomprising channels being disposed at an angle greater than 70° withrespect to a female side of the film; FIG. 1 a depicts an embodiment ofthe plastic film wherein the pressure on the male and female sides ofthe plastic film are substantially the same; FIG. 1 b depicts anembodiment of a plastic film wherein there is a greater pressure on themale side than the female side of the plastic film which is holding thechannels in a substantially closed position; and FIG. 1 c depicts anembodiment of a plastic film wherein there is a greater pressure on thefemale side than the male side of the plastic film which is opening thechannel;

FIGS. 4 a, 4 b, 4 c, and 4 d depicts portions of embodiments of aplastic film comprising female sides of the three dimensional aperturesis in the shape of slits; FIG. 4 a is a photograph of an embodimentshowing the slits; FIG. 4 b depicts an embodiment of the plastic filmwherein the pressure on the male and female sides of the plastic filmare substantially the same; FIG. 4 c depicts an embodiment of a plasticfilm wherein there is a greater pressure on the male side than thefemale side of the plastic film which is holding the channels in asubstantially closed position; and FIG. 4 d depicts an embodiment of aplastic film wherein there is a greater pressure on the female side thanthe male side of the plastic film which is opening the channel;

FIGS. 5 a and 5 b depicts a view form the female side of an embodimentof the plastic film comprising apertures in the shape of a slit; FIG. 5a shows the slit in a open position under pressure from the flow on thefemale side and FIG. 5 b shows the slit in a closed position with thepressure is substantially the same on either side of the plastic film;

FIG. 6 depicts a plan view of portion of an embodiment of a plastic filmcomprising a cat's eye or lens aperture from the female side;

FIGS. 7 a and 7 b depict a portion of an embodiment of a plastic film,FIG. 7 a depicts a plan view of portion the plastic film comprising anelliptical or rectangular with semicircular ends shaped apertures viewedfrom the female side; FIG. 7 b depicts an embodiment of the method offorming a screen having elliptical or rectangular with semicircular endsshaped apertures viewed from the female side;

FIG. 8 a depicts a screen that is capable of producing a section of filmhaving a section of film with 30° and 45° angle on the three dimensionalstructures on the surface of the film; FIG. 8 b depicts a crosssectional view of the screen showing apertures in the screen for formingthe apertures in the plastic film;

FIG. 9 depicts a flow sheet of an embodiment of the method of forming athin web. Wherein the preferential valves are formed directly the screenor are formed by both the screen and by tightly winding the film on thewind up roll;

FIG. 10 is a detail of the vacuum drum and screen in the embodimentshown in FIG. 9;

FIG. 11 depicts a flow sheet of an optional step wherein thepreferential valves are modified by passing the thin web through aheated nip; and

FIGS. 12 a, 12 b, 12 c, and 12 d depict various embodiments of screensthat may be used in methods of forming a thin web.

DESCRIPTION

The present invention is directed to thin webs comprising channels. Thechannels are capable of restricting flow in one direction to a muchgreater degree than other direction, such as by comprising preferentialflow valves. In one embodiment, a thin web comprises a plurality ofchannels extending through the film. The channels may have a male sideand a female side and are typically in a substantially closed position,however, are capable of being in an open position to allow flow from thefemale side through the film to the male side. Such channels may act aspreferential flow valves in the thin web.

Embodiments of the thin web may be useful as a separator in a containerthat is comprises two sections. Such a container could be used toseparate a liquid from a solid such as fresh fruit from its juice andprevent the liquid from substantially returning to the sectioncontaining the fruit. For example, as the fruit sits in the container ona shelf or in a refrigerator, juices may be released from the fruit. Asshown in FIG. 1, honey dew melon chunks 1 are in direct contact withjuice 2 that was released from the chunks 1 after processing. Fruitsitting in juice or other liquids tend to reduce the apparent freshnessand texture of the product. Additionally, the juice may contain orresult in unwanted growth of undesired microorganisms or mold. Sincethis juice was released after storing the fruit, the fruit has not beenpasteurized or other means have not been provided to prevent the growthof such undesirable microorganisms or molds.

Embodiments of the thin web may comprise channels that are typically ina closed position but a greater pressure on the female side than themale side is capable of opening the channels. Embodiments of thechannels may also be capable of being held in a closed when exposed to agreater pressure on the male side than the female side. The pressuredifferential may be as a result of weight of an inanimate object, aliving organism, any solid, liquid, and/or gas pressure or one side orthe other. For example, the greater pressure may be caused by fruit,vegetables, meat products, insects, or a liquid such as water, fruitjuice, vegetable juice, meat product juices, oils, as well as othersubstances. In one embodiment, the thin web may be used in a fruitcontainer to keep the fruit separated from the juices released as thefruit is stored. As shown in FIG. 2, a container 3 comprises a lowersection 4 and an upper section 5 separated by an embodiment of the thinweb 6 comprising channels that are typically in a closed position but agreater pressure on the female side than the male side is capable ofopening the channels. In such an embodiment, fruit 7 may be place in theupper section 5 of container 3 resting on the female side of the thinweb 6. The weight of the fruit 7 on the thin web 6 may further open thechannels to allow any liquid that may be released from the fruit to passthrough the web 6 into the lower section 4 of container 3. The lowersection 4 of the container 3 may be sized to contain all the liquid thatmay be released from fruit 7 during storage. The amount of liquid thatis released is dependent on the kind of fruit, storage temperature,ripeness of the fruit, as well as other factors. Preferential flowvalves on the thin web 6 substantially reduce the amount of liquid thatwill contact fruit 7 if container 3 is moved, tilted, dropped, jostled,by handling, transporting, serving or other acts.

However, without this web 6 if container 3 is moved, tilted, dropped, orjostled, the juices in the bottom section 4 may contact fruit 7 in theupper section 5 causing transfer of any microorganisms or mold to thefruit. Embodiments of the thin web 6 significantly reduce thepossibility of juices transferring from lower section 4 to the uppersection 5 and potentially contaminating fruit 7. In FIG. 2, the freshcut cantaloupe chunks 7 are held above the juice that was released fromthe cantaloupe 5 during storage. The container 3 comprises a separationlayer comprising an embodiment of the thin web 6 of the presentinvention. The cantaloupe will remain fresher and safer for consumptionfor a longer period when it is not in contact with juice or otherliquid.

FIGS. 3 a, 3 b, and 3 c depict portions of embodiments of a thin webcomprising channels being disposed at an angle greater than 70° withrespect to a female side of the film. FIG. 1 a depicts an embodiment ofa thin web 10 wherein the pressure on the male side 15 and female side16 of the thin web 10 are substantially the same. The sidewall 13 ofchannel 12 forms a flap 14 that is in a substantially closed position.Embodiments of the thin web have a memory that returns the web the flap14 substantially to its original position after distortion of the web bya force such as a differential pressure or the weight of an object onthe film. Of course, if a sufficiently strong force is exerted on thefilm, permanent deformation may occur. FIG. 3 b depicts a portion of anembodiment of thin web 10 wherein there is a greater pressure on themale side 15 than the female side 16 of the thin web 10. Thisdifferential pressure is holding the channel 12 in a substantially moreclosed position than the channel 12 in FIG. 3 a. FIG. 3 c depicts aportion of an embodiment of a thin web 10 wherein there is a greaterpressure on the female side 16 than the male side 15 of the thin web 10.A differential pressure in this direction, opposite to the direction ofFIG. 3 b, act to at least partially open the channel to allow fluids orgases to more easily pass through the web.

FIGS. 4 a, 4 b, 4 c, and 4 d depict portions of embodiments of a thinweb comprising female sides of the three dimensional apertures are inthe shape of a slit. FIG. 4 a is a photograph of an embodiment of thethin web showing the slits. FIG. 4 b depicts a portion of an embodimentof the thin web 20 comprising a female side 26 of channels 22 is in theshape of a slit wherein the pressure on the male side 25 and female side26 of the thin web 20 is substantially the same. A majority of thechannels 22 are in a substantially closed position, but are capable ofbeing in an open position to allow preferential flow from the femaleside through the film to the male side. The channels 22 are capable ofbeing in an open position by deformation of the thin web, such asdeformation by a differential pressure or weight of an object or liquidon the surface of the film. Preferably, the channels 22 of the web 20are capable of being in an open position by a higher pressure orplacement of an object or fluid on the female side 26 of the web. FIG. 4c depicts an embodiment of a thin web 20 wherein there is a greaterpressure on the male side 25 than the female side 26 of the thin web 20.In this embodiment, the higher pressure on the male side 25 tends tohold the channels 22 in a substantially closed position. FIG. 4 ddepicts a portion of an embodiment of a thin web 20 wherein there is agreater pressure on the female side 26 than the male side 25 of the thinweb 20. The higher pressure on the female side 25 causes the channels toopen more thereby allowing liquids or other objects to pass through thechannels 22.

The channels in the thin web may have any desired shape. The aperturesare typically generally circular and, thus, the channel formed isgenerally cylindrical or conical in shape. However, the shape of theapertures and the channels can be any desired shape such as slit, oval,ellipsoidal, cat's eye, lens, rectangular with semicircular ends, andother shapes may be used. In addition, multi-sided shapes such as atriangular, rectangular, square, hexagonal or a pentagonal can beutilized for the openings to form the channel. If desired, any of theshapes of the apertures may have rounded corners to ease the productionof the film. The apertures may be any size and have any desired aspectratio (the ratio of major axis to minor axis), however, in someembodiments it may be advantageous for the aspect ratio of the aperturesbe in the range of from 4:1 to 2:1. More specifically, and in someembodiments comprising a cat's eye, lens, oval or rectangular shape withsemicircular ends, it may be advantageous for the aspect ratio of theaperture to be about 3:1. In the embodiment wherein the aperture is aslit, the aspect ratio 8 may be greater than 4:1. A further feature ofthe channel of embodiments of the preferential flow valve is that thechannels may have an opening on the female side that is larger than anopening on the male side of the thin web. The larger opening on thefemale side may allow liquids to preferentially flow from the femaleside to the male side.

It may also be desirable in certain embodiments of the channel tocomprise a flap. If the channels are disposed at an angle greater than70° with respect to a female side of the film the sidewall of thechannel may be considered to be a flap. A channel having a flap may beformed directly from the shape of the aperture in a screen or formedfrom the shape of the screen and a supplemental treatment such asfolding the flap over in a nip, such as a heated nip or by tightlywinding the web on a winding roll. Such a shape is an example of apreferential flow valve formed in the thin web.

The thin web may comprise a plastic or polymer and may be a plasticfilm. The plastic film may be any suitable material such as a plastic orthermoplastic film, such as a thermoplastic polyolefin. The polyolefinmay comprise at least one of polyethylene, polypropylene, low densitypolyethylene, or high density polyethylene.

FIGS. 5 a and 5 b depict views from the male side of an embodiment ofthe aperture in the shape of a slit. FIG. 5 a shows a slit 50 in bothplan view and a cross-sectional view in an open position under pressurefrom the flow or the female side. FIG. 5 b shows the slit 50 both planview and a cross-sectional view in a closed position with the pressureis substantially the same on either side of the plastic film or thepressure is higher on the male side of the film.

FIG. 6 depicts a plan view of portion of an embodiment of a plastic filmcomprising a cat's eye or lens aperture from the female side. Theembodiment shows one pattern that may be used to design the screenwherein a pattern array is established by a square imposed in the arrayas shown. The square maybe any size, in the embodiment of FIG. 6 thesquare is 62.5 mils. Additional patterns or spacing may be used asdesired. The patterns and spacing will affect the open area of the thinweb.

FIGS. 7 a and 7 b depict a portion of an embodiment of a plastic film,FIG. 7 a depicts a plan view of portion the plastic film comprising anelliptical or rectangular with semicircular ends shaped apertures viewedfrom the female side. In the embodiment of FIG. 7 a the apertures are0.06″ wide and 0.192″ wide. The apertures are spaced apart by 0.125″ asshown. FIG. 7 b depicts an embodiment of the method of forming a screenhaving elliptical or rectangular with semicircular ends shaped aperturesviewed from the female side. The end mill may enter the screen materialat one point and move horizontally through the material to form theaperture of the desired shape or the thread mill may be moved verticallyinto and out of the material several times to form the aperture.

FIG. 8 a depicts a screen that is capable of producing a section of filmhaving a section of film with 30° and 45° angle on the three dimensionalstructures on the surface of the film. FIG. 8 b depicts a crosssectional view of the screen showing apertures in the screen for formingthe apertures in the plastic film;

Referring to FIGS. 9 and 10, an embodiment of an apparatus for themethod of the forming the thin web comprises a rotary cylindrical drum90. The cylindrical surface 93 of drum 90 comprises apertures to allowgases or liquids to flow from outside drum 90 to inside drum 90. Ascreen 94 is mounted on the surface 93 of drum 90 and rotates with thedrum 90.

Screen 94 may be a cylinder that may be slipped on the drum 90 from anend or screen 94 may be wrapped around drum 90 and then affixed in anysuitable manner. Various configurations of screens that may be used inembodiments of the present invention, some of which are described inU.S. Pat. No. 5,897,543, which is hereby incorporated by reference inits entirety. As shown in FIG. 9, a vacuum is created in the vacuumchamber 95 of drum 90 to cause a pressure differential between theinside and outside of the drum 90. A plastic sheet or a molten plasticfilm 98A is laid on the screen 94 and the differential pressure deformsthe plastic film 97 into the apertures of the screen and causes similarapertures to be formed in the film.

The vacuum chamber 95 is positioned within drum 90 and opens at thesurface of the drum over a limited portion of its periphery. Two plates95A may be used to define the vacuum chamber 95. In order to provide aneffective seal of the leading and trailing edges of vacuum chamber 95,seals 96 are typically provided in plates 95A. The seals may be made ofmetal, HDPE, rubber or other suitable material. The plates 95A arestationary with respect to the rotational direction of the drum remainin a fixed or stationary position in drum 90. Thus, vacuum chamber 95 issealed except the peripheral openings on drum 90 and may be evacuated orreduced in pressure by pumping equipment connected to the chamber in anysuitable manner.

An extruder 101 may located adjacent to drum 90 having a die which isused to extrude a hot web 97 onto screen 94. Polyolefins may be used fora thermoplastic film that may be extruded onto screen 94. The web 97contacts screen 94 which is turning with drum 90. The rotating screen 94carries sheet 97 over vacuum slot 95 which causes the web orthermoplastic film to be drawn into the openings in screen 14 andthereby apertured.

Optionally, from roll 99 the vacuum formed film 98 may continue to aroll and to corona treating roll 102. The corona treating roll 102 isusually covered with a suitable dielectric material such as epoxy,fluorinated polyethylene, chlorinated polyethylene, or polyester.However, bare roll treating with a dielectric covered electrode can beutilized to treat a film. The electrode or corona bar 103 is suspendedparallel to the treating roll 102 at about 1/16 of an inch above theroll 102. The corona bar 103 is energized by a transformer and coronatreating power source 104. The sheet may continue past a tension roll105 to a second tension roll 106 and onto wind-up roll 107. It should beunderstood that the corona treating operation is not required forembodiments of the method of forming the web. Further, it is not alwaysnecessary to wind the web onto a wind-up roll 107 if the web is beingput into an end use application in an in-line process. However, windingthe web tightly on a windup roll may urge the preferential flow valveinto more of a closed position and produce a web with a better memoryfor a closed position. As such, the web 98 may be tightly wound on thewind-up roll 107. Winding the film tightly may curve the channels orflaps of the film further into a closed position.

It should be noted that other forming processes can be utilized to formthe perforated plastic films of the present invention. The process shownin U.S. Pat. No. 4,878,825 which utilizes a support for the formingscreen in the area of the vacuum slot works particularly well in formingthe perforated film of the present invention. The process shown in U.S.Pat. No. 4,839,216 that utilizes a high-pressure liquid stream toperforate a plastic film can be also used with the present invention.The teachings of U.S. Pat. Nos. 4,878,825 and 4,839,216 are herebyincorporated by reference into this patent application as alternativemethods for forming the perforations of the present invention.

Embodiments of the plastic films may have capillaries that are disposedat an angle that acts to restrict the flow of liquids in one directionthrough the apertures. Accordingly, the films will have a characteristicsuch that fluids that pass through one direction and restricted inpassing through one direction are restricted in passing through theplastic film in the reverse direction. The degree of restriction throughthe film will be affected by the angle of the capillaries in the film,their length and the degree to which the capillaries converge in shape.The plastic film of the present invention reduces the amount of thefluid will pass through the channels by splashing.

FIGS. 12 a, 12 b, 12 c, and 12 d depict embodiments of a screen that maybe used in methods of forming a thin web. FIG. 12 a depicts a crosssection of a screen comprising an aperture having a step taperedprofile. The step taper of the aperture in FIG. 12 a is shown to besymmetrical and have even steps. Neither of these properties arerequired and the cross section of the aperture may be asymmetric or haveany desired step size. FIG. 12 b depicts a cross section of a screencomprising an aperture having a covered tapered profile. Embodiments ofthe wall profile of the curved taper aperture may be any curved shapeincluding portions of circular, elliptical, parabolic, spine curve, orany other curve. Curve sections may also be combined with linear profileof the step type to form a hybrid wave, or be a convex or concave. FIG.12 c shows an embodiment of a block profile without a taper. FIG. 12 ddepicts a cross section of a screen having a conical wall profile. Theconical profile may comprise a truncated cone (as shown in FIG. 12 d),funnel shape (such as combining a conical profile and a black profile),or a started conical shape. The profiles illustrated are merely examplesand may be modified in embodiments of the thin web.

An additional step may be incorporated into the embodiment of theinvention shown in FIGS. 9 and 10. As shown in FIG. 11, the method mayfurther include a step wherein the vacuum formed film 98 is passedthrough a nip 110 comprising at least one heated roller 111. The secondroller 112 may be non-heated. This step causes the valve flaps 113 orchannels 114 to assume a more permanent memory of being in a closedposition. The memory in the film 98 causes the channel 114 and 114A torevert to the closed position after the differential pressure or othermotive force is released.

Whereas compression of the channel in film 98 in the windup roll 107also affects the memory position of the channels 114, compression relieson creep to occur in the plastic to set the channel in a closed memoryposition. Applying heat in the nip 110 of a heated roller 111 and 112softens the polymer such that it will respond more effectively to thestresses applied to in between the rollers, or by other means, to causeit to adopt the new structural memory position 113A and 114A.

In one embodiment of the method of forming the plastic film, the film 98passes through the nip 110 of the heated roller 111 with the flap 113 orchannel 114 pointing away from the nip such that the end of the flap 113or channel 114 enters the nip 110 last. By entering the nip 110 in sucha direction the flap 113 or channel 114 will be pressed down toward thefilm 98 effectively to a substantially closed position of the flap 113Aor channel 114A. This will cause the finished angle of the channel tobecome greater than 70 regardless of the initial angle of the filmformed by the screen in the vacuum forming process.

EXAMPLE 1

A plastic jar with a screw-on lid was modified to provide a reversibleflow container. A piece of plastic film is screwed into the lid. Abeaker was filled with tap water to 150 ml line. Upon pouring the waterinto the device a stop watch is started. When the water has drained tothe line denoting 100 ml of evacuation, the stop watch is stopped andthe time, in seconds, was recorded. Five different film sample areas aretested to derive the averages above.

The drain portal is 1.75 inches in diameter or 2.4 square inches ofarea. By converting ml to Fluid Ounces the above average flow rates arecalculate.

Prior Art Ellipsoidal Loft, mils Flow Side, seconds Closed Side, seconds43.5 0.8  7.4  Flow Side, Fl Oz/sec-in² Closed Side, Fl Oz/sec-in² 1.760.19 Inventive Preferential Flow Film Loft, mils Flow Side, secondsClosed Side, seconds 30.7 5.8 20.6 Flow Side, Fl Oz/sec-in² Closed Side,Fl Oz/sec-in² 0.24 0.07

EXAMPLE 2

Faucet Drip Test: A faucet was set for dripping at 50 ml in 10 seconds(5 ml/sec). Film comprising preferential flow valves was placed over abeaker in the flow side and the closing side position. Beaker was placedunder the faucet with valve angle pointing south. Beaker was tilted Westat approximately 5° so the water could flow off if it did not penetratethe film layer. The film-covered beaker was exposed to the dripping for10 seconds.

Film comprising ellipse shaped valve Valved Cell Features and DimensionsGauge Fluid Performance Air Porosity Air Porosity Major Axis Minor AxisBasis Wt Faucet Drip* Faucet Drip* Loft Flow Side Closing Side Flow SideFlow Side (Film Gauge) Flow Side Closing Side (μm) (CFM) (CFM) (mm) (mm)(GSM) (gms) (gms) 1 709 161 102 6.58 4.40 37.9 37.3 8.5 2 687 172 986.82 4.69 36.3 7.6 3 627 182 101 6.69 4.74 41.8 3.8 Avg 674 172 100 6.704.61 37.9 38.5 6.6 St Dev 42.4 10.5 2.1 0.1 0.2 2.93 2.495

A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the scope of the invention. Accordingly,other embodiments are within the scope of the following claims.

1. A thin web, comprising: a plurality of channels extending through thefilm, wherein the channels have a male side and a female side, thechannels are substantially in a substantially closed position and arecapable of being in an open position to allow flow from the female sidethrough the film to the male side.
 2. The thin web on claim 1, wherein agreater pressure on the female side than the male side is capable ofopening the channels and a greater pressure on the male side than thefemale side is capable of holding the channels in a substantially closedposition.
 3. The thin web on claim 2, wherein a greater pressure iscaused by at least one of the weight of a solid, the weight of a liquid,or gas pressure.
 4. The thin web on claim 3, wherein the greaterpressure is caused by the weight of a solid and the solid is a fruit,vegetable, meat product, or an insect.
 5. The thin web on claim 4,wherein the greater pressure is caused by the weight of a liquid and theliquid comprises at least one of water, fruit juice, vegetable juice,meat product juices, or oils.
 6. The thin web of claim 1, wherein afemale side of at least a portion of the three dimensional apertures isat least one of a generally elliptical shape, generally circular shape,or a generally rectangular shape with semicircular ends.
 7. The thin webof claim 6, wherein the apertures have a major axis and a minor axis andthe ratio of the major axis to the minor axis is from 4:1 to 2:1.
 8. Thethin web of claim 7, wherein ratio of the major axis to the minor axisis about 3:1.
 9. The thin web of claim 1, wherein a female side of atleast a portion of the three dimensional apertures is in the shape of aslit.
 10. The thin web of claim 1, wherein a female side of at least aportion of the three dimensional apertures is in the shape of a cat'seye or lens.
 11. The thin web of claim 10, wherein the apertures have amajor axis and a minor axis and the ratio of the major axis to the minoraxis is from 4:1 to 2:1.
 12. The thin web of claim 11, wherein ratio ofthe major axis to the minor axis is about 3:1.
 13. The thin web of claim10, wherein at least one pointed end of the cat's eye or lens isrounded.
 14. The thin web of claim 1, wherein the web is one of aplastic film or a thermoplastic film comprising a polyolefin.
 15. Thethin web of claim 14, wherein the polyolefin comprises at least one ofpolyethylene, polypropylene, low density polyethylene, or high densitypolyethylene.
 16. The thin web of claim 1, wherein an opening on thefemale side is larger than an opening on the male side.
 17. The thin webof claim 1, wherein at least a portion of a sidewall of the channel actsas a flap to maintain the channels in a substantially closed position.18. The thin web of claim 17, wherein an opening on the female side islarger than an opening on the male side.
 19. A thin web, comprising: aplurality of three dimensional apertures extending through the plasticfilm, wherein the apertures form a substantially closed channel definedby a sidewall, the channels being disposed at an angle greater than 70°with respect to a female side of the film.
 20. The thin web of claim 19,wherein a female side of at least a portion of the three dimensionalapertures is at least one of a generally elliptical shape, generallycircular shape or a generally rectangular shape with semicircular ends.21. The thin web of claim 20, wherein the apertures have a major axisand a minor axis and the ratio of the major axis to the minor axis isfrom 4:1 to 2:1.
 22. The thin web of claim 21, wherein ratio of themajor axis to the minor axis is about 3:1.
 23. The thin web of claim 19,wherein a female side of at least a portion of the three dimensionalapertures is in the shape of a slit.
 24. The thin web of claim 19,wherein a female side of at least a portion of the three dimensionalapertures is in the shape of a cat's eye or lens.
 25. The thin web ofclaim 24, wherein the apertures have a major axis and a minor axis andthe ratio of the major axis to the minor axis is from 4:1 to 2:1. 26.The thin web of claim 25, wherein ratio of the major axis to the minoraxis is about 3:1.
 27. The thin web of claim 24, wherein at least onepointed end of the cat's eye or lens is rounded.
 28. The thin web ofclaim 19, wherein the thin web is one of a plastic film or athermoplastic film comprising a polyolefin.
 29. The thin web of claim28, wherein the polyolefin comprises at least one of polyethylene,polypropylene, low density polyethylene, or high density polyethylene.30. The thin web of claim 19, wherein a female side of the threedimensional apertures is in the shape of a circle.
 31. A method offorming a thin web, comprising: passing a thin web through a heated nip,wherein the thin web comprises three dimensional apertures and the nipis sufficiently hot to deform the apertures.
 32. The method of claim 31,wherein the three dimensional apertures of the thin web are disposed atan angle from about 5° to about 60° with respect to a plane that isperpendicular to a surface of the thin web.
 33. The method of claim 31,wherein the apertures are deformed to be disposed at an angle fromgreater than 70° with respect to a plane that is perpendicular to asurface of the thin web.
 34. The method of claim 31, wherein the nip isheated above the softening temperature of the thin web.